The present invention relates to a seal pattern in a liquid crystal device (xe2x80x9cLCDxe2x80x9d), and more particularly to a dummy seal pattern in a LCD for use within a fiber optical device.
LCDs are widely used in a broad range of consumer electronics and display systems. A conventional LCD includes an upper substrate having a common electrode, a lower substrate having pixel electrodes, thin film transistors, metal wiring, and other well-known components for activating the pixel electrodes, a seal pattern that seals the upper and lower substrates with a predetermined gap therebetween, and a liquid crystal material that fills the gap.
FIG. 1 is a plan view of conventional LCD 10. Active area 12 is formed in a central region of substrate 14. The elements necessary for operation of LCD 10 are provided on active area 12 of LCD 10. Primary seal pattern 16 is also formed on lower or upper substrate 14 and substantially surrounds around active area 12. Typically, seal pattern 16 is disposed at a predetermined distance from active area 12.
Liquid crystal injection port 18 is formed through seal pattern 16. End seal 19 seals injection port 18. Seal bar 17 can be formed between liquid crystal injection port 18 and active area 12 and prevents end seal 19 from penetrating into the interior of seal pattern 16. Seal pattern 16, seal bar 17, and end seal 19 have a predetermined height that corresponds to the gap between the upper and lower substrates and can be formed from an adhesive insulating epoxy or any other appropriate bonding material. The bonding material can also include a plurality of spherical spacers for helping to ensure a uniform gap between the upper and lower substrates.
LCD 10 can be constructed by bonding an upper substrate (not shown) having a common electrode to lower substrate 14 via seal pattern 16 and/or seal bar 17. After the substrates are bonded together, a vacuum is normally applied in the gap formed between the upper and lower substrates and within seal pattern 16. Once a vacuum is formed, a liquid crystal material is normally injected into the gap through injection port 18. After injection, liquid crystal injection port 18 is typically sealed with end seal 19.
Foreign matter, such as dirt, chemical residues, and other contaminants, can destroy the integrity of seal pattern 16 and diminish the quality of the LCD. The foreign matter can be deposited on seal pattern 16 or on the inner surfaces of the upper and lower substrates when the gap formed between the substrates is under vacuum.
FIG. 2 shows LCD 10 after additional outer seal pattern 15 has been added to prevent the effects of broken seals. Outer seal pattern 15 surrounds inner seal pattern 16 and generally follows the shape of seal pattern 16. The presence of second seal pattern 15 prevents the liquid crystal material from leaking when the seal of first seal pattern 16 is broken. Therefore, the distance between first seal pattern 16 and second seal pattern 15 is normally chosen to be sufficiently large such that if first seal pattern 16 is broken, such as when pressure is applied to the upper substrate during the bonding process, second seal pattern 15 does not also break.
Although double sealed systems are less fragile than single seal systems, these LCD are still susceptible to breakage and warping.
FIG. 3 shows a side cross-sectional view of another conventional LCD 20. LCD 20 includes upper substrate 21 and lower substrate 22, which are bonded together using seal pattern 24. During cell construction, seal pattern 24 is provided on one of the substrates and spacer 26, which includes a plurality of particles, is provided on the other substrate. The two substrates are then normally attached to each other and liquid crystal material 28 is injected therebetween. The presence of spacer 26 during attachment, however, expels liquid crystal material 28 and creates localized defects about the individual spacer particles, which typically have a diameter on the order of about tens of microns. When the LCD is used as a display device, the defects do not significantly degrade the performance of the LCD system because the defects are relatively small and undetectable by a naked human eye.
When the LCD is used in other applications, however, such as along the optical path of a fiber optic system, the presence of the spacer particles in the optical path can significantly degrade the performance of the system. For example, the diameter of a core of a single mode fiber can be less than 10 microns. Also, when a beam of light exits such a fiber, a collimated beam can be formed that has a diameter of approximately 400 microns. In either case, the presence of defects in the LCD caused by spacers in the optical path can significantly alter the intensity and polarization state of the propagating light, such as by scattering the incident light.
It would therefore be desirable to provide one or more clear optical paths through an LCD having a uniform gap.
It would also be desirable to provide an LCD that includes a minimum number of localized defects and provides a clear optical path for use with fiber optic systems.
It would further be desirable to provide an LCD in which the liquid crystal material is uniformly distributed in the LCD""s active area.
It is therefore an object of this invention to provide one or more clear optical paths through an LCD having a uniform gap.
It is also an object of the present invention to provide an LCD that includes minimum number of localized defects and provides a clear optical path for use with fiber optic systems.
It is a further object of the present invention to provide an LCD in which the liquid crystal material is uniformly distributed in the LCD""s active area.
In accordance with this invention, an LCD is provided that has a seal pattern formed between the substrates of a liquid crystal device is provided. The seal pattern can include: (1) a primary seal pattern that substantially surrounds the active area and (2) a dummy seal pattern formed at least partially inside the primary seal pattern.
The dummy seal pattern includes a plurality of discontinuous seal portions. These seal portions can be disposed on the substrate in the form of one or more lines, or randomly in any desirable pattern. The seal portions can also have the same or varying sizes, shapes, and orientations.
A fiber optic device that includes an LCD having a dummy seal pattern is also provided.